Cell-mediated cytotoxicity, as mediated by lymphoid populations from alloimmune and tumor-bearing animals, will be investigated using the lectin-dependent cell-mediated cytotoxicity assay. In vivo and in vitro experiments are proposed to examine the nature of the effector cell, the ability of various lectins to participate in the reaction, and the conditions required for the induction and expression of cytotoxic reactivity. In addition, the effect of tumor cell immunogeneicity and tumor burden on direct and lectin-dependent cytotoxicity will be studied. A preliminary investigation of the immunotherapeutic effectiveness of combined lectin administration and alloimmunization is proposed.